1. Field of the Invention
This invention relates in general to magnetic recording systems, and more particularly to magnetic recording systems that use side-by-side thin film head designs.
2. Description of Related Art
Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modern personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.
Many important advances have been made that provide higher data density and thus increased storage capacities for storage systems. These advances include faster access speeds and faster access times resulting in a greater bandwidth of data communicated to and from the storage systems. Advances have also been made by greatly reducing the size and weight of the storage systems, resulting in the availability of ultra-light portable computers having state-of-the art capabilities and performance.
A disk drive is one example of a magnetic storage system. A disk drive storage system, for example, uses a rotatable disk with concentric data tracks containing information, a head for reading and/or writing data onto the various tracks, and an actuator connected to a sensor for moving the sensor to a desired track and maintaining the sensor over the track centerline during read and write operations. The sensor is suspended in close proximity to a recording medium. For example, the sensor may be suspended over a magnetic disk having a plurality of concentric tracks. Another type of magnetic storage system includes a magnetic tape system. However, storage systems are not limited merely to the above-mentioned magnetic storage systems.
Disk drive storage systems utilize thin film head designs that are mostly variations of a merged design or a piggyback design. The merged design, as well as the piggyback design, places a write element atop a read sensor. In these dual-element designs, an inductive coil element used for writing and a magnetoresistive (MR) element used for reading are spaced apart from one another in a direction perpendicular to the trailing end of the merged head.
A problem with dual-element heads is commingling of magnetic fields. For example, the magnetic field from an inductive write element can alter the magnetization state of a nearby magnetoresistive read element because the read and write elements are closely spaced relative to one another. This may produce unwanted magnetic instability in, for example, the read head functionality. Moreover, some magnetic flux does flow though the second shield (S2) and magnetoresistive layers even with increases in shield thickness and element separation.
Another drawback of the merged and piggyback designs is that the write head is positioned far from the large thermal heat sink of a thin film head's slider. Accordingly, the placement of write coils relative to a read head causes unwanted thermal effects prolonging heat dissipation. Also, the write head protrudes towards the air-bearing surface (ABS) causing a greater read element-to-ABS distance.
Side-by-side dual-element heads have been proposed to address these problems. In a side-by-side head, the write gap and the magnetoresistive sensing film of the MR read element are located in the same plane of the slider but are spaced apart from one another in a direction parallel to the slider trailing end. In this design, the read and write elements are not simultaneously located over the same track so it is necessary for the actuator to move the slider if read and write operations are to take place sequentially on the same track.
The side-by-side design may eliminate the magnetic coupling between the read and write heads and diminish the write head's protrusion (e.g., by placing the coils much closer to the slider). However, this design results in a loss of recorded density because of a very large separation between the read and write head pole tips; as separation and isolation between the read and write head poles increases, the loss of recorded density (i.e., transducer's ability to sense and write distinguishable transitions) increases.
One reason for this loss of recorded density is that the inside and outside tracks recorded onto a recording medium, such as a disk, are controlled by the placement of the read or write head in the side-by-side dual-head configuration. Accordingly, the total number of written tracks is reduced because the actuator positions one of the read or write poles of the side-by-side head closer to the inside or outside of the disk than the other head (at the limit of rotary travel). The head closest to the center of the disk, as viewed when the actuator is at the actuator's inner and outer limits on the disk surface, limits the ability of one side-by-side read or write head to read and write to both the innermost and outermost tracks. Accordingly, a loss of recorded density results from this inability to read and write to these innermost and outermost tracks.
Another concern in side-by-side thin film head designs is the fabrication process. In any manufacturing operation, yield converts directly to profit. High yields are essential in real-time cost recovery for the billion-dollar fabrication lines of today. In the fabrication of thin film heads, there are two critical features, the width of the read sensor (MRw) and the width of the write pole tip (P2w), to determine areal density. Areal or bit density of a write head indicates the number of bits that can be written to a square inch of magnetic media, such as a magnetic tape or magnetic disk.
In the fabrication of a prior art thin-film inductive head, a first pole piece layer (P1) is deposited on a substrate. A write gap layer is deposited over the P1 layer, wherein the write gap layer greatly affects the linear resolution of a recording head. A coil layer is then formed over the write gap layer and a second pole layer (P2) is formed over the coil layer.
The second pole piece layer is the most demanding structure in the whole fabrication process. The second pole piece layer is the most demanding structure because the width of the second pole piece layer (P2w) is critical to determining the width of a written track. Accordingly, if the P2 layer is fabricated poorly, reworking of the head becomes extremely difficult and the head may have to be discarded. Discarding the heads results in a process yield loss, which directly relates to a loss in profit.
It can be seen that there is a need for a method and apparatus for a side-by-side thin film head with minimal separation between the read and write structures.
It also can be seen that there is a need for a method and apparatus for fabricating thin film inductive heads that can be reworked with a minimum yield loss.